A so-called drum type or front loading type of spin extractor is constituted so that the laundry is loaded in a basket drum having a horizontal rotation axis, and that the drum is rotated about the axis at high speed. One of the serious problems with this type of spin extractor is that, when the drum is rotated at high speed with the laundry distributed unevenly on its peripheral wall, abnormal vibration or noise occurs due to the unbalance in mass distribution around the central axis of the drum. For suppressing such vibration or noise, some of the conventional washing/drying machines having the above type of spin extractor have one or several weight pieces attached to an outer tub in which the drum is mounted. This type of washing/drying machine, however, is very heavy and large, so that it is difficult to move or transport it, and its installation is limited.
Some proposals have been made addressing this kind of abnormal vibration or noise of the drum type spin extractor. For example, the Publication No. H6-254294 of the Japanese Unexamined Patent Application discloses a spin extractor wherein the drum is rotated at low speeds for redistributing the laundry on the inner peripheral wall of the drum before the drum is rotated at a high speed for liquid extraction. In detail, the speed of the drum is controlled by a two-stage balancing operation including steps of rotating the drum at a first low speed for a short time and then rotating the drum at a second low speed that is a little higher than the first low speed and much lower than the high speed for extraction.
In addition, the above spin extractor has a vibration sensor on its base as a means for detecting the eccentric load due to an uneven distribution of the laundry in the drum. When the vibration sensor detects abnormal vibration during the rotation of the drum at high speed, the drum speed is reduced.
By the above-described method of controlling the drum speed, however, it is not assured that the laundry is redistributed evenly on the inner peripheral wall of the drum by a single cycle of the two-stage balancing operation. Therefore, the balancing operation often becomes a trial and error process including steps of rotating the drum at the low speeds for correcting the balance, raising the drum speed to the high speed for extraction and, responsive to a detection of abnormal vibration, reducing the drum speed to rotate the drum at the low speeds again. If such a trial and error process occurs, the time required for the extraction becomes very long.
Besides, none of the conventionally proposed methods of correcting the balance of the laundry effectively works when only one or a few large articles, such as a bed sheet, are loaded in the drum, because this type of article is hard to loosen when it retains water and forms a larger mass.